This invention lies in the field of voltage clamp circuits in which a load current is switched on and off. Each time the load current is switched off, high voltage transients are generated due to the load and parasitic lead and wiring inductance. This invention provides a method of clamping this voltage to a preset acceptable level by providing a low power feedback circuit to the switch control logic to momentarily turn the switch back on long enough to dissipate the stored energy through the switch itself. This is accomplished by using inexpensive components in the feedback circuit and the switch itself to protect against high voltage spikes during turn off.
The prior art of this type of invention uses such techniques as a "Clamping Diode" across the load, an "RC Clamp Network" across the switch or an "RC Snubber" across the switch. All of these methods have various shortcomings which this invention overcomes. The primary advantage, however, is that the prior art requires, in addition to a switch capable of handling the voltage and currents of the load, a completely separate circuit to clamp the voltage spikes generated at turnoff. These separate circuits must be rated at the same voltage and current handling capabilities as the switch itself. This results in a duplication of power handling devices in the circuit and, thus, a duplication of costs for the more expensive power devices in the circuit.